In the production of continuous buttweld pipe, strip stock, known as skelp, is fed from a coil, through a heating furnace, and then through a forming and welding mill. In the forming and welding mill, the red hot skelp is first formed into a tube, in a multiple stand forming mill, and then the opposite edges of the skelp are brought together under pressure to form a weld.
Properly formed and buttwelded tubing typically is conveyed from the continuous buttweld mill to a stretch reducing mill, in which the pipe is subjected to a combination of rolling pressure and longitudinal tension, to produce a finished pipe having desired diameter and wall thickness characteristics. On the downstream side of the stretch reducing mill, there is typically provided a flying hot saw, which severs the stretch reduced pipe to the desired length, after which the individual lengths are conveyed to a cooling bed. All of the foregoing is well known and conventional.
In the initial start up of the continuous buttweld mill, a considerable amount of scrap pipe is produced while the skelp is being brought up the proper welding temperature. Where a stretch reducing mill is employed downstream of the forming and welding mill, it is not feasible to permit the scrap pipe to enter the stretch reducing mill, because of possible damage to the mill. Accordingly, it is necessary for the scrap portions of the pipe to be cut off and removed between the forming and welding mill and the stretch reducing mill. In the past, this has necessitated a considerable amount of heavy manual work, typically with the use of torches to cut the scrap into sections, which are then manually dragged out of the way and eventually picked up for reprocessing. Where a stretch reducing mill is not employed in the line, it is sometimes possible to utilize the regular production flying cut-off saw to sever the scrap sections during start up. However, even this is sometimes not possible, and in all events a substantial amount of heavy manual work is required in handling and removing the scrap sections severed by the production saw.
Pursuant to the invention, a novel and improved scrap saw is provided, which is suitable for installation downstream of the forming and welding mill (and upstream of a stretch reducing mill, if used). The scrap saw of the invention includes a rotary frame mounted above the pass line and carrying cutting saws at each of two ends, such that two cuts may be made for each revolution of the frame. This is particularly desirable in the handling of scrap, inasmuch as it permits the scrap to be severed into short, easily manageable lengths, while still permitting the rotary saw frame to be rotated at appropriately low speeds.
In accordance with one feature of the invention, the dual rotary saws are driven by a stationary drive motor, located on the main frame of the equipment. This enables a significant reduction in the weight of, and a corresponding simplification of the rotating parts of the saw mechanism.
Pursuant to another specific aspect of the invention, the individual saw blade mechanisms are supported by spaced inboard and outboard frame housings, which are fixed to a common shaft and mounted for rotation in unison. One of the frame housings encloses a drive train for rotating the saw blades, while the other housing encloses an orienting mechanism for maintaining the saw blades in a vertical plane at all times.
A synchronous cam arrangement is provided for supporting the pipe directly underneath the cutting area of the saw blades. The cam is arranged to rotate in accordance with the rotations of the saw frame, such that the pipe is engaged and raised into cutting position as a saw blade moves through the lowermost portions of its arc.
In accordance with another feature of the invention, the entire scrap saw mechanism is mounted on slideways, for movement between operative and retracted positions. When the mechanism is in its operative or working position, it is clamped securely to its slideways, for maximum rigidity of the mounting. For retracting and advancing movements, the clamping facility is released.
In the system of the invention, there is included an advantageous kick-out arrangement in the pipe conveying system, downstream of the scrap saw, enabling the short, cut-off scrap sections to be kicked out of the conveyor line and discharged into a reception bin.
Rotary saws in general are, of course, well known. Representative of the prior art, in this respect, are the Garling U.S. Pat. No. 1,923,261, the Passoni U.S. Pat. No. 3,207,020, and the Pferdekaemper U.S. Pat. No. 3,267,785. Thus, the present invention is not directed broadly to the concept of a rotary saw, but more specifically to structural features of a rotary saw which enable a dual or multiple saw mechanism to be provided, which is practical for utilization in the described environment.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.